1. Field of the Invention
The present invention relates to a ball joint in which a rod is affixed in a socket of synthetic resin, the ball of the ball stud is maintained so that it cannot come out of the socket and the ball stud can be freely swung relative to the socket.
2. Description of the Prior Art
There have been examples of ball joints such as the one described by Japanese Patent Publication No. 60-9450, which comprises a rod having an annular groove at one end; a stud having a ball on one end; a socket of synthetic resin in which the ball stud is swingably affixed, the socket having an annular groove provided on the inside surface of a hole into which an end of the rod is inserted, the groove tapering outward in the direction in which the rod is inserted; and a ring which fits into the groove in the socket and engages with the groove in the rod to prevent the rod being withdrawn from the hole. In the ball joint thus configured, the ring is contracted to insert it into position in the groove of the socket, and the end of the rod is then inserted into the rod hole in the socket, which expands the ring and allows the insertion of the rod into the hole. Once the rod has been inserted, the resilience of the ring causes it to snap into engagement with the groove on the rod, thereby maintaining the rod so it does not come back out of the socket.
Another example of a ball joint that is known, described in JP-A-59-69518, is comprised of a rod having a male thread on one end, a ball stud, and a synthetic resin socket in which the ball stud is swingably affixed and which has a rod fixing hole the inside surface of which is provided with a female thread for engagement with the male thread of the rod. In this ball joint arrangement the rod is affixed to the socket by the screwed engagement of the male thread of the rod with the female thread of the socket.
With the former ball joint arrangement, the annular groove has to be formed by undercutting the inside surface of the hole into which the rod is inserted. This presents a problem, as it is difficult to form the socket and the undercut portion. A problem with the latter ball joint arrangement is the screw engagement of the rod with the socket, which makes assembly a time-consuming process and requires the use of a complex mold, increasing the cost. In addition, because rotation of the rod could cause the rod to become unscrewed and disengage from the socket, some means of preventing this has to be used, such as using adhesive to bond the rod and socket together, for example.
An object of the present invention is to provide a ball joint having a straightforward structure, in which the socket can be readily formed and the operation of affixing the rod in the socket can readily be accomplished.